Judges has been quite the emotional roller-coaster. Every time you think it can't get more depraved and bloody, it just keeps getting worse.
The first thing we have to realize is despite the title, the "judges" are not in fact judges but war-leaders. Every one of the judges in the text has daring, bloody exploits, and not one of them is shown leading the country in peace-time. In fact, the judges in the book are mostly not the sort of people you'd want ruling you in peace-time: most of them seem to have some pretty deep psychological problems.
The book of Judges is covers 400 years of wars, both foreign and civil. For every hero who charges off and defeats the massed hordes of Midianites with a force of only 300 men (Gideon, Judg. 7), there's another depraved soul who kills his 70 half-brothers and slaughters Israelite villages (Abimelech, his son, Judg. 8). For every cunning, who-would-have-seen-it-coming underdog who takes down a fat, self-righteous king (Eglon, Judg. 3; Jael, Judg. 4-5), there's a tribe who decides to use force of arms to take down their fellow Israelites and conquer their land (Dan, Judg. 18). It's not a pretty picture.
Judges also shows us how some Genesis stories might have turned out if God didn't step in at the last minute to save the day. We know that God tested Abraham's faith by telling him to kill his son, Isaac. (Gen. 22) But every Bible-school-child knows that God stayed Abraham's hand at the land minute and had Abraham sacrifice a ram instead. Jephthah, in Judg. 11, doesn't get that lucky. He promises to sacrifice the first thing that greets him after his victorious conquest against the Ammonites. When that "thing" turns out to be his only daughter, his only child, God doesn't tell Jephthah to stop. He is forced to complete the sacrifice so that all Israel will mourn his daughter until the end of time.
Similarly, God saves Lot from sodomy in Gen. 19. He even saves Lot's two virgin daughters from being deflowered by the mob. For their crimes, God strikes the men of Sodom blind, and then destroys their city. In Judg. 19, a Levite in the same situation doesn't have that deus ex machina. Instead, the mob rapes his concubine all night, and God does nothing to stop it. The Levite eventually goes home, kills his wife, and sparks the biggest civil war in the whole book, nearly wiping out the entire tribe of Benjaminites.
As the text is constantly reminding us, there were no kings at this time, and every man did as he wished. The author seems to be blaming these horrid episodes on the lack of a monarch: if only there were a king, this wouldn't have happened. But, as we'll see starting in the next book big (Samuel), Israel doesn't become much better once they do have a king. It's enough to make you start questioning human nature... or at least what makes compelling literature.